Resistance of fiber-reinforced fly ash-steel slag based geopolymer mortar to sulfate attack and drying-wetting cycles

Fly ash-steel slag based geopolymer mortar was studied for recycling solid wastes and developing a sustainable alternative to Ordinary Portland Cement (OPC). The fiber-reinforced geopolymer mortar was prepared from the main raw materials of fly ash, steel slag, and fibers. This paper studies the mechanical properties, mass loss rates and appearance of fiber-reinforced geopolymer under double-factor coupling, i.e. sulfate corrosion and drying-wetting cycle process on the geopolymer samples. The results show that the compressive strength and flexural strength of each sample gradually increase and tend to be stable under double-factor coupling. After 15 cycles, the compressive strength of the SF-4 (mixed with 0.4 vol% steel fiber) is still the highest, which is 67.9 MPa, and the compressive strength of the BF-3 (mixed with 0.3 vol% basalt fiber) increases the most, whose growth rate is 96.6%. Due to the evaporation of water and diffusion of sodium sulfate between samples and solution, the change of mass loss rate of samples was unstable. The white precipitate was observed on the surface of samples, and it was sodium sulfate by X-ray diffraction (XRD) analysis. Both stable and dense structures of samples and fiber-bridged matrix function make fiber-reinforced geopolymer mortar present excellent performance in resistance to double-factor coupling corrosion. (C) 2020 Elsevier Ltd. All rights reserved.